Designing an integrated circuit (IC) that has both low current consumption, such as about 100 nano-Amps (nA) to about three micro-Amps (μA), and has high voltage capability, such as about 24 V to about 42 V, while also being robust with respect to electromagnetic compatibility (EMC) has proven challenging in the industry. Desire for such an IC exists for sensor ICs, automotive ICs, industrial ICs and others.
Challenges in such circuits arise from the need for the regulation or control of a high-voltage transistor. Such a transistor can protect the circuit from high voltages and provide EMC immunity but also needs a start-up or bias current, which is desired to be avoided for low power consumption. Further, a starting resistance connected to the external high voltage is also needed, but this resistance is typically large, such as about 420 Mega-Ohms (MΩ) at about 42 V and 0.1 μA, and therefore itself consumes a significant current. At low voltages, such as about 2.5V, and high temperatures, the start-up current is too small with respect to the leakage current, such as less than 50 nA.
While these problems can be avoided in some conventional implementations by standby operation of analog and digital circuits, such implementations require external standby signals and pins. These standby signals and pins are not possible or practical in many applications, and some applications, such as stand-alone sensors, require autonomous wake-up operation. Additionally, while some sensor IC implementations use a standby and awake cycle operation, these are typically low-power sensors and thus are not capable of the desired higher voltages.
Therefore, a need remains for an IC that has both low current consumption and a high voltage capability while also being robust with respect to EMC.